The invention relates to a well-treating or operating process for measuring patterns or profiles of temperatures with distances within intervals of subterranean earth formations which can be long, deep and hot. More particularly, the invention relates to installing and operating equipment for obtaining such information in an economically feasible manner, particularly while a well is being operated as a temperature observation well or is being heated or utilized in a manner affecting the temperature in and around the well.
Various temperature measuring processes have been described in patents. U.S. Pat. No. 2,676,489 described measuring both the temperature gradient and differential at locations along a vertical line in order to locate the tops of zones of setting cement. U.S. Pat. No. 3,026,940 discloses the need for heating wells for removing paraffin or asphalt or stimulating oil production and describes the importance of knowing and controlling the temperature around the heater. It uses a surface located heater arranged to heat portions of oil being heated by a sub-surface heater, with the control needed to obtain the desired temperature at the surface located heater being applied to the sub-surface heater.
Various temperature measuring systems involving distinctly different types of sensing and indicating means for use in wells have also been described in U.S. patents. For example, patents such as U.S. Pat. Nos. 2,099,687; 3,487,690; 3,540,279; 3,609,731; 3,595,082 and 3,633,423 describe acoustic thermometer means for measuring temperature by its effect on a travel time of acoustic impulses through solid materials such as steel. U.S. Pat. No. 4,430,974 describes a measuring system in which a plurality of long electrical resistance elements are grouted in place within a well and sequentially connected to a resistance measuring unit to measure temperature or fluid flow.
U.S. Pat. No. 3,090,233 describes a means for measuring temperatures within a small reaction zone, such as one used in a pilot plant. A chain drive mechanism pushes and pulls a measuring means such as a thermocouple into and out of a tube extending into the reaction zone while indications are provided of the temperature and position within the tube.
In some respects, the present invention amounts to a modification of the system described in U.S. Pat. No. 3,090,233. The prior system mechanically pushed and pulled a relatively stiff measuring assembly and suggested no way in which a temperature sensing means, such as a thermocouple, could be moved for significant distances up and down within a well. But, Applicants have discovered with a certain combination of elements measurements can be made within subterranean earth formation intervals while are relatively very deep, very long, and very hot. This requires a combination of a long measuring means conduit, an electrically responsive temperature sensing means which telemeters electrical responses along a metal sheathed telemetering cable which is heat stable, a flexible weighting means connected below the sensing means and a means for spooling the telemetering cable and requires that those elements be arranged to have physical and chemical properties which are properly interrelated. In addition, Applicants found that in contrast to previously described methods for measuring sub-surface temperatures within wells, the presently described interrelated combination of elements is particularly beneficial in being capable of providing substantially equilibrated temperature measurements from all points along a long interval of subterranean earth formations without involving any more man hours than are needed for the quick scan of a computer printout. In contrast, the prior methods for obtaining such temperature logs have required continual attendance, and delayed well operation, for days or weeks.